1. Field of the Invention
The present invention relates to a game apparatus and a computer-readable recording medium recording a game program which are used to execute a game utilizing a gyroscopic sensor and an acceleration sensor. More particularly, the present invention relates to a game apparatus and a computer-readable recording medium recording a game program which are used to detect a motion applied to an input device and reflect the detected motion on a game process.
2. Description of the Background Art
Conventionally, an input control device for a game apparatus is known that includes a gyroscopic sensor and an acceleration sensor (e.g., Japanese Patent Laid-Open Publication No 2000-308756). The input control device is in the shape of a bar, and is moved as if it were a sword. A game process is executed, depending on the motion. In this game process, data corresponding to a motion of the sword (i.e., an intensity, and forward, backward, leftward, rightward, upward and downward movements, etc.) is created based on an output of the acceleration sensor. Also, data corresponding to an attitude of the sword that is rotated (turned) or tilted forward, backward, leftward or rightward is created based on an output of the gyroscopic sensor. Based on the thus-created data, a movement of an object (in this case, a sword) in a game is displayed on a game screen of a monitor.
However, a game process employing an input control device as described above has the following problems. Firstly, each motion of the input control device is detected based on an output of only either the acceleration sensor or the gyroscopic sensor. In other words, a motion of a sword is detected based on only an output of the acceleration sensor, while an attitude of a sword is detected based on only an output of the gyroscopic sensor.
When a motion of a sword is detected based on only an output of the acceleration sensor, it is difficult to correctly detect a change in attitude of the input control device while it is moving. It is possible to calculate an attitude of the acceleration sensor at rest, assuming that an output of the sensor is a gravitational acceleration. However, when the sensor is moving, an acceleration due to a motion as well as the gravitational acceleration are added to the output of the sensor, and therefore, it is difficult to calculate the attitude. Also, since the direction of the gravitational acceleration is no longer available, it is even not difficult to determine the direction of a motion. Therefore, for example, when the input control device (sword) is moved downward on a zigzag path (see FIG. 31), then if an attitude of the input control device is changed at the turning points of the path, such a change cannot be detected. Therefore, in this case, it is no longer possible to determine the actual direction of the moving sword. In other words, a gesture of the player cannot be correctly represented as a motion of a sword.